Center punch



1950 A. HOWARD ETAL 2,519,908

CENTER PUNCH Filed March 29, 1949 INVENTUHS ARI: HI E HOWARD WALTER L. MORRIS UN A T TUHNEY Patented Aug. 22, 1950 UNITED STATES PATENT OFFICE This invent-ion relates to center punches for use in pattern plate transfers, and has for its object to provide a device of this type whereby the center markings upon a work piece from a pattern having holes of different diameters can be rapidly and easily accomplished in a simple manner,

Another object of this invention is to provide a marking device in which the operation of entering it into the pattern hole and applying pressure will automatically adjust it to its centering position with respect to the work material.

Gther objects of the invention relate to the structural features resulting in a simple device of the fewest possible parts, economically produced, easily assembled and convenient to use.

Our invention is illustrated in the accompanying drawing, in which Fig. 1 is a fragmentary side elevational view of the device in normal position.

Fig. 2 is an end view of Fig. 1.

Fig. 3 is a cross-sectional view taken upon line 33 of Fig. 1.

Fig. 4 is a fragmentary side elevational view of the device in operated position.

Fig. 5 is an end view of the parts as shown in Fig. 4.

Fig. 6 is a fragmentary view with parts in section showing a modification of the device of the invention in normal position in a hole of a pattern plate, and

Fig. 7 is a view of the parts shown in Fig. 6 with the device expanded.

As shown in the drawings, a tubular member 5 of resilient metal is divided at one end into a plurality of resilient arms 6 by means of slits I extending for a distance longitudinally of the tube 5. In its portion beyond the ends of the slits, the tubular member 5 is provided with a knurled portion 8.

Located in the tubular member 5, and longitudinally movable therein, is a punch rod II] of hardened steel. Upon its lower end, the punch rod I is formed with an enlarged tapered collar member I I, and a prick punch extension I2.

At its upper end, the punch rod ID extends beyond the end of the tubular member 5, and is screw-threaded, as at I3, to receive a screwthreaded head I4, which provides a tapping surface for a hammer. The head is provided with a knurled surface I for easy handling.

At their lower ends, each of the resilient arms 6 is provided on its inner surface with a bevel or chamfer as indicated at I6 (Fig. 3). This bevel is of the same taper as the taper on the 2 Claims. (Cl. 33191) 2 collari I so that it will ride easily over the collar when tnetubaiar member and the punch rod are moved relative to each other;

In the smaller sizes of punches, the eutsise di-v ameter er the tubular member 5 may be substan tiaiiy the same as the greatest diameter of the collar EI on the punch rd as shown in 6. This relation of the parts insures that the lower ends or the resilient members may be entered in a hole of sufficient diameter to receive thd'lang est diameter of the tapered collar, thus adapting it to smaller holes.

In the modification shown in Figs. 6 and 7, a work plate 20, which is to be marked, is shown below a pattern plate 2I, which is provided with a hole 22, to be centered upon the work plate 20'. In Fig. 6, the device is shown in its normal position in the hole 22 of the pattern plate 2|, in which position there will be a clearance between the peripheral portions of the arms 6 and the inner diameter of the hole 22. By applying downward pressure to the tubular member 5, the ends of the resilient arms will be expanded over the tapered portion II of the punch rod I0 until the outer surfaces of the resilient arms 6 will engage the inner surface of the pattern hole 22. In the position of the parts, a hammer tap on the head l4 will produce the desired drilling center.

In the modification illustrated in Figs. 6 and '7, the outside diameter of the tubular member 5, with the resilient member 6 in normal position, is the same as the largest diameter of the tapered collar I I on the punch rod II]. This provides a structure which will accommodate itself to holes of less diameter than will the structure shown in Figs. 1 to 5.

The punch rod I0 fits snugly in the upper end of the tubular member 5, but slides easily therein so that it is always accurately centered within the tube.

The device is characterized by its simplicity of operation, which adapts it to rapid and accurate transfer work.

It is apparent from the construction that the simple acts of inserting the device into a hole until the lower end of the punch rod rests upon the work plate, followed by sliding the tubular member 5 downwardly upon the punch rod to expand the ends of the arms '6 to engage the periphery of the hole of the pattern, will accurately determine the location for the punch mark.

This obviously is a one handed operation and may be performed as rapidly as the tool can be moved from one hole to the other and struck with the hammer.

A single punch may be made to handle holes 01! different diameters. For example, a tool which will center for a hole one-eighth of an inch in diameter, may center for all sizes of holes between one-eighth and three-sixteenths of an inch. Larger punches will have a wider range. For example, a punch with a minimum of one inch may also serve to center a hole one and onehalf inches in diameter.

The punch rod may be easily replaced in case the marker point becomes dulled or broken.

Although we have shown and described our invention with respect to certain details of construction, it is to be understood that we do not wish to be unduly limited thereto, certain variations from the disclosure being possible without departing from the spirit or scope of our invention.

We claim:

1. In a transfer punch, a tubular member of resilient material slitted longitudinally for a portion of its length to form a plurality of resilient strips, a punch rod longitudinally movable within the tubular member, a tapered collar on the lower end of the punch rod bearing against the inner faces of the resilient strips at their ends to expand them outwardly against the bore of a hole upon longitudinal movement of the tubular member, and a prick punch formed upon the outer face of the collar.

2. A centering punch for transfer marking comprising in combination a punch rod provided on one end with a tapered collar having a maximum diameter greater than the diameter 01 the body portion of the rod, a head secured to the opposite end of the rod, and a tubular member of substantially the same outside diameter as the largest diameter of the tapered collar slidable upon the rod, said tubular member being longitudinally slitted for a portion of its length to provide a plurality of resilient members adapted to be spread apart by longitudinal sliding engagement with the collar on the punch rod.

ARCHIE HOWARD. WALTER L. MORRISON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

